In a battle between two teams vying for eighth in the Eastern Conference (yup, you read that right), the Celtics blew a 16-point lead but salvaged the night when Ray Allen sandwiched a fast-break layup and two free throws around a big Kevin Garnett offensive rebound in the final minute to secure an 86-83 win over the Cavaliers.

Allen (22) and Garnett (18) combined for 40 points to help the Celtics (16-17) avoid the first six-game losing streak of the new Big Three era and stretch their lead over the Cavs (13-19) to 2.5 games for the eighth seed.

WHAT WENT RIGHT

Welcome back Bass: The Celtics finished 1-5 in Bass’ recent six-game absence, and it didn’t take long for the consistent big man to demonstrate his value on the court, scoring 10 points on six shots by halftime. Bass brings a combination of scoring and toughness that the C’s simply don’t have outside of Garnett. If the Celtics have any hope for success in the second half of the season, they need a healthy Bass contributing like this.

Nothing but Garnett: Garnett reportedly called a team meeting prior to the All-Star break, and even if the entire team didn’t respond in its first game since, at least KG came to play. Wincing at times, possibly still battling the hip injury that kept him out of a game before the break, Garnett totaled 18 points and eight boards while playing his usual staunch defense. In the final seconds with the C’s leading by one, Garnett willed an offensive rebound off his own miss, got fouled and made both foul shots.

Jumping the run: Perhaps the result of an aging team benefiting from the five-day NBA All-Star break, the Celtics rattled off runs of 9-0 and 13-0 in the first quarter to establish a rare double-digit lead early (28-15 after one). Rondo recorded six assists in the first 12 minutes, including one on another fast break with his new running mate Chris Wilcox. The have only led after the first quarter in 16 of their 33 games, accumulating a 12-4 record.

If Danny Ainge shook a Magic 8-Ball right now, the odds of “outlook not so good” coming up are probably even. After losing seven of their past eight games for the first time since he acquired Kevin Garnett and Ray Allen prior to the 2007-08 NBA season, Ainge’s aging Celtics are 15-17 entering the All-Star break.

It’s an uphill battle the rest of the season, but it might be all downhill from here for Doc Rivers & Co. Needless to say, based on the expectations they’ve set the past four years, this Celtics group isn’t making the grade. Let’s take a look at how the C’s have stacked up individually this year.

When the news broke that Jeff Green would undergo heart surgery for an aortic aneurysm, the Celtics once again had a hole to fill behind Paul Pierce at the small forward position. Pietrus has bridged that gap, and then some. Charged with 3-point shooting and bringing energy defensively, he has shot 36.4 percent from beyond the arc and defended vigorously (at the end of the blowout loss to the Thunder, Pietrus was one of few C’s who played to the buzzer). In an attempt to improve the team’s terrible rebounding, Pietrus has also begun to assert himself on the glass, grabbing 19 rebounds in his last two games.

KEVIN GARNETT: A-Last Grade: B+

Of the aging Big Three, the one with the most mileage and the worst knees has enjoyed the best season. Garnett entered the NBA All-Star break by recording 23 points and 13 rebounds for the first time since December 2008. That marked his ninth double-double of the season, bringing his averages to 14.4 points and 7.9 rebounds in only 30.8 minutes. Paired with his usual defensive prowess, he’s played all but three games — missing only one due to a tweaked hip and two for personal reasons — and it’s no surprise the Celtics are 0-3 in those contests.

Following a 89-73 loss to the Mavericks, the Celtics dropped to 15-16 and the Eastern Conference’s eighth seed (just two games ahead of the lowly Cavaliers) — the worst start to any season of the Kevin Garnett era.

Should all be unavailable in the team’s final game before the All-Star break, the C’s starting center midway through the 2011-12 season will come down to a choice between rookies Greg Stiemsma and JaJuan Johnson. Generally, that’s the kind of thing that happens when a team enters the year with an injury-plagued 15-year veteran as its only established center. Not to mention Kendrick Perkins will be starting for the opposing team.

In some respect Celtics president Danny Ainge had to see this coming, although nobody could have expected them to be this bad. Here are five shockingly awful statistics the 2011-12 Celtics have produced.

While the Celtics rank eighth in field-goal percentage (45.8%), they’re 26th in points scored. Why? Two reasons: They don’t get to the free throw line, and they don’t attempt enough 3-pointers.

To the first point, free throws are down across the NBA, but the Celtics have been particularly inept in that regard. The C’s are one of only two teams that attempt fewer than 30 field goals per game from 0-10 feet, where the majority of fouls occur. Only the Nets (8-21) take fewer shots within 10 feet (27.9) than the Celtics (29.5). From 2007-10, when the C’s made two trips to the NBA Finals, they averaged more than 25 free throws per game and ranked in the NBA’s top 10 each season. This season, they attempt just 19.8 a night.

That last number has gotten increasingly worse as this season has progressed. The C’s nightly free throw attempts have declined from 23.8 in December to 20.2 in January and an NBA-worst 16.4 in February. For the season, the Celtics are being outscored by an average of 2.2 points per game at the free throw line.

Ever since he first arrived in New England as a University of Connecticut freshman in 1993 (the same year he became a Patriots fan, by the way), Celtics guard Ray Allen‘s work ethic has remained as steadfast as Fort Independence. Even now, after three years of college, 15 NBA seasons and about 3.5 million shots, his role continues to mutate annually — but his approach never will.

“Every year, no matter what team I played on, my role changes,” said the 36-year-old Allen. “You come to training camp, even when I was in Milwaukee, you change things and the league changes a little bit, so you have to figure out how different you’re going to play and you’re going to be played and guarded defensively. I always just said, well, let’s see how everything works and how it goes.”

So far, so good. Before being traded to Boston, Allen had built a Hall of Fame career during 11 seasons on the Bucks and SuperSonics, averaging at least 20 points, four rebounds and three assists for 10 straight years before being dealt for Delonte West, Wally Szczerbiak and Jeff Green during the 2007 NBA draft.

Joining forces with fellow superstars Paul Pierce and Kevin Garnett under head coach Doc Rivers, Allen like the others had to sacrifice numbers for the greater good of the team. In his first season on the Celtics, his attempts dipped by 7.5 field goals per game while his shooting percentages rose across the board.

“When I got here, that was extremely hard, because I wanted to do more,” he said. “I still want to do more, but then I was going off what I’d done my whole career, so I wanted to come here and do the same thing. But in order for this team to be successful I had to take a couple step backwards to fit in a system where it’s going to work, because it wasn’t built around me. That’s just being part of a team and trying to win on your team’s terms and not yours.”

Mickael Pietrus isn’t Ray Allen, even though he played him on TV Friday night — starting in place of the injured NBA 3-point champion for the second straight night. And he knows he isn’t Celtics teammate Paul Pierce either.

“That man been a 10-time All-Star,” Pietrus said of Pierce. “I’d love to be Paul PIerce, but I’m Mickael Pietrus. … I’m happy to get Paul back. It was hard for me to guard him on the opposing team. I’m glad I’m his teammate. It’s Paul Pierce. He’s a 10-time All-Star. He knows how to play basketball.”

Pietrus knows how to play basketball, too, and he’s filled in admirably for Allen. In back-to-back starts against the Magic and Pacers, he has totaled 25 points — including five 3-pointers — and 12 rebounds.

‘He’s been huge,” said Pierce. “You talk about a guy who can really knock down shots and make plays. He’s a really scrappy defender and a great athlete. He’s been huge in Ray’s absence, just filling in that role and being that constant threat from the outside and filling in gaps on defense.’